Reactivity of Osmium(VI) Nitrides with the Azide Ion. A New Synthetic Route to Osmium(II) Polypyridyl Complexes

Article abstract of DOI:10.1021/ic9800280

There is an extensive reactivity chemistry between trans-[Os^VI(tpy)(Cl)₂(N)]⁺ (1) (tpy = 2.2′:6′,2″-terpyridine) and N₃^-. Reaction of 1 with N₃^- in CH₂C1₂ or acetone occurs by electron transfer to give trans,trans-(tpy)(Cl)₂Os^II(N₂)Os ^II(Cl)₂(tpy). In CH₃CN, trans-Os^II(tpy)(Cl)₂(N₂) forms but undergoes solvolysis to give transOs^II(tpy)(Cl)₂(CH₃CN). 1 reacts with excess N₃^- in CH₃CN to give Os^III(tpy)(Cl)₂(5-CH₃-tetrazolate), which has been characterized by X-ray crystallography. This is the first known Os-tetrazolato complex. 1 reacts with N₃^- in the presence of CS₂ to give trans-[Os^II(tpy)(Cl)₂(NS)]⁺, SCN^-, and N₂.

Full text of DOI:10.1021/ic9800280

3610
Inorg. Chem. 1998, 37, 3610-3619
Reactivity of Osmium(VI) Nitrides with the Azide Ion. A New Synthetic Route to
Osmium(II) Polypyridyl Complexes
Konstantinos D. Demadis, Thomas J. Meyer,* and Peter S. White
Venable and Kenan Laboratories, Department of Chemistry, CB 3290, University of North Carolina at
Chapel Hill, Chapel Hill, North Carolina 27599-3290
ReceiVed January 8, 1998
There is an extensive reactivity chemistry between trans-[OsVI(tpy)(Cl)2(N)]+ (1) (tpy ) 2,2′:6′,2′′-terpyridine)
and N3-. Reaction of 1 with N3- in CH2Cl2 or acetone occurs by electron transfer to give trans,trans-(tpy)(Cl)2-
OsII(N2)OsII(Cl)2(tpy). In CH3CN, trans-OsII(tpy)(Cl)2(N2) forms but undergoes solvolysis to give trans-
-
OsII(tpy)(Cl)2(CH3CN). 1 reacts with excess N3 in CH3CN to give OsIII(tpy)(Cl)2(5-CH3-tetrazolate), which
has been characterized by X-ray crystallography. This is the first known Os-tetrazolato complex. 1 reacts with
N3 in the presence of CS2 to give trans-[OsII(tpy)(Cl)2(NS)]+, SCN-, and N2.
-
cation; S ) solvent; tetr ) tetrazolate anion; TBAH ) tetra-n-
butylammonium hexafluorophosphate; DMF ) dimethylformamide;
DMSO ) dimethyl sulfoxide.
Introduction
In an earlier communication we reported that an extensive
chemistry exists between the azide ion (N3-) and the OsVI
nitrido, trans-[OsVI(tpy)(Cl)2(N)]+, 1a (tpy ) 2,2′:6′,2′′-terpyr-
idine).1 In this manuscript we present a full account of this
reactivity which includes formation of terminally bound N2 OsII
and OsIII nitriles, OsII thionitrosyls, and OsIII tetrazoles, as well
as one-electron transfer and coupling to give a µ-N2 dimer. This
adds to the existing chemistry of 1a which includes trans f
cis isomerization,2 reversible 4e-, 3H+ reduction to OsII
ammine,3 oxo transfer from OdNMe3 to give OsII nitrosyl,4
nucleophilic attack by PR3 to give OsIV phosphoraniminato,5
and one-electron reduction of 1a, followed by N-N coupling
to give an OsII(N2)OsII dimer.6
Materials. Acetonitrile (CaH2) and dichloromethane (P2O5) were
dried and distilled under argon and were subsequently deoxygenated
by purging with nitrogen prior to use. DMF was distilled from CaH2
under reduced pressure. DMSO was used as received. Deuterated
solvents and isotopically labeled reagents were purchased from
Cambridge Isotope Laboratories and used as received. TBAH was
recrystallized three times from boiling ethanol and dried under vacuum
at 120° for 2 days. All nitriles were obtained from Aldrich and used
without further purification. HBF4‚Et2O was purchased from Aldrich
and stored in a refrigerator.
Physical Measurements and Instrumentation. Electronic absorp-
tion spectra were recorded on Beckman 2000, OLIS-modified Cary
14, or Hewlett-Packard 8452A diode array UV-visible spectropho-
tometers in quartz cuvettes. Electrochemical measurements were carried
out in CH3CN solutions with 0.1 M TBAH as the supporting electrolyte
or in aqueous solutions of varying ionic compositions. A platinum
bead working electrode was used for measurements in CH3CN or CH2-
Cl2, and a Teflon-sheathed glassy carbon working electrode (Bioana-
lytical Systems, West Lafayette, IN) was used for measurements in
aqueous solutions. The surface of the glassy carbon electrode was
polished with diamond paste before use. All potentials are referenced
to the saturated sodium chloride calomel electrode (SSCE, 0.24 V vs
NHE), unless otherwise noted, at room temperature and are uncorrected
for junction potentials. Voltammetric experiments were performed with
the use of a PAR 173 galvanostat/potentiostat. A PAR 179 digital
coulometer was used in conjunction with a PAR 173 galvanostat/
potentiostat for coulometry experiments. Infrared spectra were recorded
as KBr pellets on a Nicolet 20DX FT-IR spectrometer.
Experimental Section
The following compounds and salts appear in this study: trans-
[OsVI(tpy)(Cl)2(N)](Cl) (1a); trans-[OsVI(tpy)(Cl)2(N)](PF6) (1b); trans-
[OsVI(tpy)(Cl)2(15N)](PF6) (1b*); cis-[OsVI(tpy)(Cl)2(N)](PF6) (1c);
trans-OsII(tpy)(Cl)2(N2) (2); trans-OsII(tpy)(Cl)2(NCCH3) (3); trans-OsII-
(tpy)(Cl)2(NCC5H6) (4); trans-OsII(tpy)(Cl)2(NCCH2CH2CH3) (5); trans-
OsII(tpy)(Cl)2(NCCHdCH2) (6); trans,trans-(tpy)(Cl)2OsII(N2)OsII(Cl)2-
(tpy) (7); trans-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (8); cis-[OsIII(tpy)(Cl)2-
(NCCH3)](PF6) (9); cis-OsIII(tpy)(Cl)2(N3) (10); trans-OsII(tpy)(Cl)2-
(py) (11); trans-OsII(tpy)(Cl)2(4-(CH3)3C-py) (12); trans-[OsIII(tpy)(Cl)2-
(5-CH3-tetrazolate) (13); trans-[OsII(tpy)(Cl)2(NS)](SCN) (14); trans-
[OsII(tpy)(Cl)2(15NS)](SCN) (14*); cis-[OsII(bpy)2(Cl)(NCCH3](PF6)
(15).
Abbreviations used in the text include the following: tpy ) 2,2′:
6′,2′′-terpyridine; bpy ) 2,2′-bipyridine; py ) pyridine; PPN ) bis-
(triphenylphosphoranylidene)ammonium cation; Fc+ ) ferrocenium
Synthesis and Characterization of Compounds and Salts. The
salts trans-[OsVI(tpy)(Cl)2(N)](Cl) (1a),2 trans-[OsVI(tpy)(Cl)2(N)](PF6)
(1b),2 trans-[OsVI(tpy)(Cl)2(15N)](PF6) (1b*),3 cis-[OsVI(tpy)(Cl)2(N)]-
(PF6) (1c),2 trans-[OsIV(tpy)(Cl)2(NPPh3)](PF6),5 and cis-[OsII(bpy)2(Cl)-
(NCCH3)](PF6) (15)7 were prepared according to literature procedures.
Bis(triphenylphosphoranylidene)ammonium Azide, (PPN)N3. This
reagent was prepared by mixing equimolar amounts of (PPN)Cl and
NaN3 in EtOH. Stirring for 5 h, filtration (to remove NaCl), evaporation
of the solvent, and recrystallization from CH3CN/Et2O afforded a white
powder in nearly quantitative yield. Infrared (cm-1, KBr disks): ν-
(N3) 2013, ν(PdN) 1114.
(1) Demadis, K. D.; El-Samanody, E.-S.; Meyer, T. J.; White, P. S. Inorg.
Chem. 1998, 37, 838.
(2) Williams, D. S.; Coia, G. M.; Meyer, T. J. Inorg. Chem. 1995, 34,
586.
(3) Pipes, D. W.; Bakir, M.; Vitols, S. E.; Hodgson, D. J.; Meyer, T. J. J.
Am. Chem. Soc. 1990, 112, 5514.
(4) Williams, D. S.; White, P. S.; Meyer, T. J. J. Am. Chem. Soc. 1995,
117, 823.
(5) (a) Demadis, K. D.; Bakir, M.; Klesczewski, B. G.; Williams, D. S.;
White, P. S.; Meyer, T. J. Inorg. Chim. Acta 1998, 270, 511. (b) Bakir,
M.; White, P. S.; Dovletoglou, A.; Meyer, T. J. Inorg. Chem. 1991,
30, 2835.
Reaction of trans-[OsVI(tpy)(Cl)2(N)](PF6) (1b) with (PPN)N3. An
amount of trans-[OsVI(tpy)(Cl)2(N)](PF6) (1b, 50 mg, 75 µmol) was
(6) Demadis, K. D.; Meyer, T. J.; White, P. S. Inorg. Chem. 1997, 36,
5678.
(7) Kober, E. M.; Caspar, J. V.; Sullivan, B. P., Meyer, T. J. Inorg. Chem.
1988, 27, 4587.
S0020-1669(98)00028-7 CCC: $15.00 © 1998 American Chemical Society
Published on Web 06/24/1998

New Route to Os(II) Polypyridyl Complexes
Inorganic Chemistry, Vol. 37, No. 14, 1998 3611
dissolved in 20 mL of CH3CN, and (PPN)N3 (45 mg, 75 µmol) was
added to it immediately as a solid in small portions. Some ef-
fervescence was noted, the solution became very dark in color, and a
black powder started precipitating. After being stirred for 30 min, the
solution was filtered and the black powder was isolated. It is a mixture
of trans-OsII(tpy)(Cl)2(N2) (2, minor product) and trans-OsII(tpy)(Cl)2-
(NCCH3) (3, major product). Pure 3 can be obtained by recrystallization
from a 5:1:10 mixture of DMF/CH3CN/Et2O. Yield: quantitative. Anal.
Calcd for OsCl2N4C17H14‚DMF (MW 608.5): C, 39.44; H, 3.45; N,
11.50. Found: C, 39.06; H, 3.69; N, 11.22.
cis-OsIII(tpy)(Cl)2(15N3) (10*) was prepared by the same method
by using N3 labeled at the R-nitrogen. Infrared (cm-1, KBr disks):
-
ν(15N3) 2033.
Following the same method as above for 3 and by using the
appropriate pyridine as solvent, the following OsII pyridine complexes
were synthesized.
trans-OsII(tpy)(Cl)2(py) (11). Yield: 65%. Anal. Calcd for
OsCl2N4C20H15 (MW 573.1): C, 41.88; H, 2.62; N, 9.77. Found: C,
41.21; H, 2.78; N, 9.62.
trans-OsII(tpy)(Cl)2(tBu-py) (12). Yield: 70%. Anal. Calcd for
OsCl2N4C24H24 (MW 629.6): C, 45.74; H, 3.81; N, 8.89. Found: C,
45.17; H, 4.29; N, 9.49.
trans-OsIII(tpy)(Cl)2(5-CH3-tetrazolate) (13). Method A. trans-
[OsVI(tpy)(Cl)2(N)] (PF6) (1b, 23 mg, 35.2 µmol) was dissolved in 10
mL of CH3CN and (PPN)N3 (0.04 g, 71 µmol) rapidly added. The
solution was stirred for 3 h and filtered. Addition of 50 mL Et2O to
the filtrate caused the precipitation of a brown powder. This was
recrystallized from CH3CN/DMF/Et2O mixtures to give black crystals.
Yield: 16 mg (70%). Anal. Calcd for OsCl2N7C17H14‚DMF (MW
650.5): C, 36.89; H, 3.23; N, 17.22. Found: C, 36.29; H, 3.32; N,
16.69.
Following the same method as above for 3 and with the appropriate
nitrile as solvent gave a variety of OsII nitriles.
trans-OsII(tpy)(Cl)2(NCC6H5) (4). Yield: 58%. Anal. Calcd for
OsCl2N4C22H16 (MW 597.5): C, 44.22; H, 3.02; N, 10.57. Found: C,
43.53; H, 3.69; N, 9.73.
trans-OsII(tpy)(Cl)2(NCCH2CH2CH3) (5). Yield: 49%. Anal.
Calcd for OsCl2N4C19H18 (MW 563.5): C, 40.46; H, 3.19; N, 9.94.
Found: C, 40.31; H, 3.40; N, 9.86.
trans-OsII(tpy)(Cl)2(NCCHdCH2) (6). Yield: 90%. Anal. Calcd
for OsCl2N4C18H14 (MW 547.5): C, 39.45; H, 2.56; N, 10.23. Found:
C, 39.53; H, 2.90; N, 10.97.
trans,trans-(tpy)(Cl)2OsII(N2)OsII(Cl)2(tpy) (7). An amount of
trans-[OsVI(tpy)(Cl)2(N)](PF6) (1b, 50 mg, 75 µmol) was dissolved in
20 mL of CH2Cl2, and (PPN)N3 (45 mg, 75 µmol) was added to it as
a solid very slowly in small portions. The solution became very dark
blue in color, and a black powder started precipitating. After being
stirred for 30 min, the solution was filtered and a black powder was
isolated. It was washed with small amounts of CH3CN, CH2Cl2, and
3 × 30 mL portions of anhydrous Et2O and finally air-dried. Yield:
87%. The resulting material can be purified by recrystallization from
DMF/Et2O. Anal. Calcd for Os2Cl4N8C30H22‚2DMF (MW 1162.9):
C, 37.15: H, 3.10; N, 12.04. Found: C, 37.24; H, 3.04; N, 13.90.
Infrared (cm-1, KBr disks): ν(NtN) 2035 (vw); ν(15Nt15N) 1972 (vw);
ν(tpy) 1448 (vs), 1435 (vs), 1383 (vs). 7 can be also prepared in
excellent yields by reacting 1b with Et3N or Et4SH in CH3CN.
trans-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (8). Method A. To an
amount of trans-[OsVI(tpy)(Cl)2(N)](PF6) (100 mg, 94 µmol) was added
1 equiv of Fc(PF6) (31 mg, 94 µmol). Then, (PPN)N3 (55 mg, 94
µmol) was added to the mixture in small portions. The color changed
to brown-yellow. Precipitation with ether and recrystallization from
CH3CN/Et2O afforded a brown-black microcrystalline material.
Yield: 82%. Anal. Calcd for OsCl2BF4N4C17H14 (MW 680.3): C,
29.99; H, 2.06; N, 8.23. Found: C, 29.91; H, 1.83; N, 8.31.
Method B. An amount of trans-[OsIV(tpy)(Cl)2(NPPh3)](PF6) (100
mg, 94 µmol) was dissolved in CH3CN (40 mL), and a few drops of
HBF4×Et2O were added under vigorous stirring. The color changed
from deep brown to brown-yellow, and the reaction mixture was stirred
for 1 h. Filtration and addition of Et2O (100 mL) caused a brown
powder to precipitate. Final recrystallization from CH3CN/Et2O gave
an analytically pure material. The properties of this salt, formulated
as trans-[OsIII(tpy)(Cl)2(NCCH3)](BF4), match those of the material
from method A.
cis-[OsIII(tpy)(Cl)2(NCCH3)](BF4) (9). This salt was prepared by
following method A for trans-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (8) and
starting with cis-[OsVI(tpy)(Cl)2(N)](PF6) (1c) and Fc(BF4). Anal. Calcd
for OsCl2BF4N4C17H14 (MW 622.2): C, 32.79; H, 2.25; N, 9.00.
Found: C, 32.76; H, 2.52; N, 9.30. The cis configuration was
confirmed by X-ray crystallography (see below).
cis-OsIII(tpy)(Cl)2(N3) (10). trans-[OsVI(tpy)(Cl)2(N)](Cl) (1a, 200
mg, 0.37 mmol) was dissolved in H2O (20 mL). After being stirred
for 30 min the solution turned from pink to tan, indicating the formation
of cis-[OsVI(tpy)(Cl)2(N)](Cl) (1c). At this point, NaN3 (48 mg, 0.72
mmol) was added to it as a solid. Vigorous evolution of a gas was
observed, and the solution became dark in color, while a black powder
began to precipitate. After being stirred for 2 h the mixture was filtered
and a black microcrystalline solid was isolated. This was washed
several times with H2O and Et2O and air-dried. Yield: 154 mg (78%).
Anal. Calcd for OsCl2N6C15H11 (MW 536.4): C, 33.56; H, 2.05; N,
15.66. Found: C, 33.00; H, 2.24; N, 15.23. Infrared (cm-1, KBr
disks): ν(N3) 2041.
Method B. trans-OsII(tpy)(Cl)2(NCCH3), 3, was allowed to react
with (PPN)N3 in a 1:1 ratio in CH3CN. After the solution was stirred
for 3 h, Et2O was added to precipitate 3 as a brown solid in quantitative
yield. This compound exhibits spectroscopic characteristics identical
to the one obtained by method A.
trans-[OsII(tpy)(Cl)2(NS)](SCN) (14). A quantity of trans-[OsVI-
(tpy)(Cl)2(N)](PF6) (1b, 30 mg, 46 µmol) was dissolved in 5 mL of
acetone. To this solution was added 20 mL of CS2. A solution of
(PPN)N3 (27 mg, 46 mmol) in 20 mL of acetone was added to the
above mixture dropwise while stirring, which caused the color of the
solution to turn dark brown. The reaction mixture was stirred at room
temperature for 2 h. During that time a brown solid formed. This
solid was filtered off, washed with acetone and Et2O, and recrystallized
from DMF/Et2O to afford golden-brown crystals. Yield: 27 mg (82%).
Anal. Calcd for OsCl2S2N5C16H11 (MW 598.94): C, 32.06, H, 1.85,
N; 11.69. Found: C, 31.63, H, 2.07, N, 11.46. Infrared (cm-1, KBr
disks): ν(14NtS) 1295 (vs); ν(tpy) 1476 (vs), 1450 (vs), 1384 (vs);
ν(SCN) 2047 (vs). The salt trans-[OsII(tpy)(Cl)2(15NS)](SCN) (14*)
was prepared by the same method starting with trans-[OsVI(tpy)(Cl)2-
(15N)](PF6) (1b*). Infrared (cm-1, KBr disks): ν(15NtS) 1265 (vs).
Reaction of cis-OsIII(tpy)(Cl)2(N3) (10) with CeIV. An amount of
10 (20 mg, 37 µmol) was suspended in H2O (20 mL). To that
suspension, Ce(NH4)2(NO3)6 (41 mg, 75 µmol) was added. While the
mixture was stirred vigorously, intense bubbling was noted and the
color of the solution became tan. Stirring was continued until
effervescence ceased (1 h). The resulting solution had a UV-vis
spectrum identical with that of cis-[OsVI(tpy)(Cl)2(N)]+ (1c).2 Quan-
titation based on ꢀ ) 250 M-1 cm-1 for the absorption band at 470 nm
showed that conversion of 10 to 1c was quantitative.
X-ray Structural Determinations. Data Collection, Solution, and
Refinement of the Structures. Single crystals of 13 and 14 were
obtained by slow diffusion of Et2O into DMF solutions of the salts.
Single crystals of 9 and 15 were obtained by slow diffusion of Et2O
into CH3CN solutions of the salts. Crystal data, intensity collection
information, and structure refinement parameters for the structures are
provided in Table 1. The structures were solved by either Patterson
or direct methods. The remaining non-hydrogen atoms were located
in subsequent difference Fourier maps. Empirical absorption corrections
were applied for all structures with DIFABS or SADABS. The ORTEP
plotting program was used to computer generate the structures shown
in Figures 1-3.8 An ORTEP diagram for 13 has been published.1
Hydrogen atoms were included in calculated positions with thermal
parameters derived from the atom to which they were bonded. All
computations were performed by using the NRCVAX suite of
(8) Johnson, C. K. ORTEP: A Fortran thermal ellipsoid plot program;
Technical Report ORNL-5138; Oak Ridge National Laboratory: Oak
Ridge, TN, 1976.

3612 Inorganic Chemistry, Vol. 37, No. 14, 1998
Demadis et al.
Table 1. Summary of Crystal Data, Intensity Collection, and Structure Refinement Parameters for cis-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (9),
trans-[OsIII(tpy)(Cl)2(5-CH3-tetrazolate) (13), trans-[OsII(tpy)(Cl)2(NS)](SCN) (14), and cis-[OsII(bpy)2(Cl)(NCCH3)](PF6) (15)
compd
formula
MW
9
13
14
15
OsCl2C17H14BF4N4
622.23
OsCl2C17H15N7‚DMF
604.47
OsCl2C16H11S2N5
598.52
OsClC22H19OPF6N5‚Et2O
798.16
a (Å)
b (Å)
8.518(2)
12.234(2)
22.321(5)
13.146(2)
24.785(4)
11.766(3)
10.6156(5)
11.4668(5)
c (Å)
18.783(6)
90
92.88(2)
90
14.549(5)
90
105.37(2)
90
13.090(3)
90
104.07(2)
90
12.7977(6)
70.957(1)
85.743(2)
82.762(2)
R (deg)
â (deg)
γ (deg)
V (Å3)
1954.8(8)
4116(2)
3703(1)
1459.9(1)
Z
4
8
8
2
cryst system
space group
cryst size (mm)
monoclinic
P21/n
monoclinic
C2/c
monoclinic
C2/c
triclinic
P1h
0.4 × 0.2 × 0.1
0.15 × 0.20 × 0.45
0.08 × 0.10 × 0.50
0.20 × 0.25 × 0.10
d
calcd (g/cm3)
2.114
1.951
2.147
1.816
diffractometer
radiation
collcn temp (°C)
abs coeff µ, cm-1
F(000)
2θmax (deg)
tot. reflcns
Rigaku
Rigaku
Rigaku
Siemens SMART diffr
Mo KR (λ ) 0.710 73 Å)
-100
6.84
1178.47
46
4034
2712
1999
0.048
262
5.3
6.3
2.00
-2.750
3.580
Mo KR (λ ) 0.710 73 Å)
-100
6.47
2304.59
50
6586
3625
2860
0.038
266
3.0
3.7
1.21
-1.050
1.260
Mo KR (λ ) 0.710 73 Å)
-100
7.41
2270.41
50
3246
3246
2275
0.035
235
3.6
3.7
1.27
-0.920
1.160
Mo KR (λ ) 0.710 73 Å)
-100
4.58
779.30
60
20 666
8220
7927
0.025
370
2.3
3.0
2.01
-1.950
1.610
unique reflcns
refined reflcns
merging R value
no. of params
R (%)a
Rw (%)b
goodness of fitc
deepest hole (e/Å3)
highest peak (e/Å3)
. .
a R ) ∑(|Fo - Fc|)/∑|Fo|. b Rw ) [∑(w|Fo - Fc|)2/∑w(Fo)2]1/2 c GoF ) [∑w(Fo - Fc)2/(no. of reflections - no. of parameters)]1/2
Figure 1. ORTEP diagram (30% probability ellipsoids) for the cis-
[OsIII(tpy)(Cl)2(NCCH3)]+ cation in 9.
programs.9 Atomic scattering factors were taken from a standard
source10 and corrected for anomalous dispersion.
Figure 2. ORTEP diagram (30% probability ellipsoids) for the cis-
[OsII(bpy)2(Cl)(NCCH3]+ cation in 15.
The crystal of 13 contains one molecule of dimethylformamide per
asymmetric unit, which exhibited some disorder. This disorder was
modeled successfully. The crystal of 15 contains one molecule of
diethyl ether per asymmetric unit. The final positional parameters,
along with their standard deviations as estimates from the inverse
matrix, and tables of hydrogen atom parameters and anisotropic thermal
parameters are available as Supporting Information. Bond lengths and
angles of the compounds are given in Tables 2-5.
Results
Synthetic Studies. Addition of stoichiometric amounts of
N3 to magenta trans-[OsVI(tpy)(Cl)2(N)]+ in CH3CN causes
-
an immediate reaction that yields a mixture of products. The
minor product is 2, and the major product is 3. They form
roughly in a 1:3 ratio. Both compounds precipitate from CH3-
CN and are isolated as black powders. 2 was detected by
infrared spectroscopy from its characteristic ν(NtN) stretch at
2090 cm-1 in KBr. Allowing 1b* to react with N3- in CH3CN
(9) Gabe, E. J.; Le Page, Y.; Charland, J.-P.; Lee, F. L.; White, P. S. J.
Appl. Crystallogr. 1989, 22, 384.
(10) International Tables for X-ray Crystallography; Kynoch Press: Bir-
migham, U.K., 1974; Vol. IV.

New Route to Os(II) Polypyridyl Complexes
Inorganic Chemistry, Vol. 37, No. 14, 1998 3613
Table 4. Selected Bond Lengths (Å) and Bond Angles (deg) for
trans-[OsII(tpy)(Cl)2(NS)](SCN) (14)
Bonds
Os(1)-Cl(1)
Os(1)-Cl(2)
Os(1)-N(1)
Os(1)-N(11)
2.3663(22)
2.3600(22)
1.834(7)
Os(1)-N(22)
Os(1)-N(28)
S(1)-N(1)
2.032(7)
2.084(7)
1.459(8)
2.079(7)
Angles
Cl(1)-Os(1)-Cl(2) 174.17(8) Cl(2)-Os(1)-N(28)
Cl(1)-Os(1)-N(1)
91.04(21)
92.40(25) N(1)-Os(1)-N(11) 101.2(3)
Cl(1)-Os(1)-N(11) 89.85(20) N(1)-Os(1)-N(22) 179.7(3)
Cl(1)-Os(1)-N(22) 87.67(20) N(1)-Os(1)-N(28) 102.9(3)
Cl(1)-Os(1)-N(28) 89.11(21) N(11)-Os(1)-N(22) 78.6(3)
Cl(2)-Os(1)-N(1)
Cl(2)-Os(1)-N(11) 87.63(20) N(22)-Os(1)-N(28) 77.4(3)
Cl(2)-Os(1)-N(22) 86.68(21) Os(1)-N(1)-S(1) 178.5(5)
93.24(25) N(11)-Os(1)-N(28) 155.9(3)
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
cis-[OsII(bpy)2(Cl)(CH3CN)](PF6) (15)
Bonds
Os(1)-Cl(1)
Os(1)-N(1)
Os(1)-N(11)
Os(1)-N(21)
2.4199(6)
2.0187(22)
2.0755(21)
2.0365(21)
Os(1)-N(31)
Os(1)-N(41)
N(1)-C(2)
2.0440(21)
2.0477(21)
1.143(3)
Figure 3. ORTEP diagram (30% probability ellipsoids) for the cation
trans-[OsII(tpy)(Cl)2(NS)]+ in 14.
C(2)-C(3)
1.455(4)
Angles
Table 2. Selected Bond Distances (Å) and Bond Angles (deg) for
cis-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (9)
Cl(1)-Os(1)-N(1)
Cl(1)-Os(1)-N(11)
90.24(6) N(11)-Os(1)-N(31) 176.63(8)
96.02(6) N(11)-Os(1)-N(41) 99.85(8)
Cl(1)-Os(1)-N(21) 173.66(6) N(21)-Os(1)-N(31) 98.65(8)
Bonds
Cl(1)-Os(1)-N(31)
Cl(1)-Os(1)-N(41)
N(1)-Os(1)-N(11)
N(1)-Os(1)-N(21)
N(1)-Os(1)-N(31)
86.96(6) N(21)-Os(1)-N(41) 89.47(8)
88.74(6) N(31)-Os(1)-N(41) 78.59(8)
Os(1)-Cl(1)
Os(1)-Cl(2)
Os(1)-N(1)
Os(1)-N(11)
2.346(4)
2.354(4)
2.039(13)
2.072(12)
Os(1)-N(22)
Os(1)-N(28)
N(1)-C(2)
1.995(12)
2.063(12)
1.102(21)
1.46(3)
85.62(8) Os(1)-N(1)-C(2)
92.10(8) N(1)-C(2)-C(3)
178.74(22)
177.7(3)
C(2)-C(3)
95.98(8) Os(1)-N(11)-C(12) 125.66(18)
Angles
91.84(15) Cl(2)-Os(1)-N(28) 100.8(3)
N(1)-Os(1)-N(41) 174.52(8) Os(1)-N(11)-C(16) 115.86(17)
N(11)-Os(1)-N(21) 78.30(8) C(12)-N(11)-C(16) 118.12(22)
Cl(1)-Os(1)-Cl(2)
Cl(1)-Os(1)-N(1) 179.8(4)
Cl(1)-Os(1)-N(11) 92.3(4)
Cl(1)-Os(1)-N(22) 87.6(4)
Cl(1)-Os(1)-N(28) 87.3(3)
N(1)-Os(1)-N(11)
N(1)-Os(1)-N(22)
N(1)-Os(1)-N(28)
N(11)-Os(1)-N(22) 79.3(5)
N(11)-Os(1)-N(28) 158.7(5)
N(22)-Os(1)-N(28) 79.4(5)
Os(1)-N(1)-C(2)
N(1)-C(2)-C(3)
87.8(5)
92.6(5)
92.7(5)
Information. An attempt to separate neutral 2 and 3 by selective
crystallization from DMF/CH3CN mixtures resulted in loss of
N2 from 2 and isolation of pure 3 in quantitative yields. On
the basis of these observations, it appears that the initial reaction
Cl(2)-Os(1)-N(1)
87.9(4)
Cl(2)-Os(1)-N(11) 100.4(4)
Cl(2)-Os(1)-N(22) 179.4(4)
-
with N3 forms the N2 complex, followed by solvolysis,
174.9(13)
178.8(17)
[OsVI(tpy)(Cl)2(N)]+ + N3- f OsII(tpy)(Cl)2(N2) + N2 (1)
OsII(tpy)(Cl)2(N2) + S S ) solvent8 OsII(tpy)(Cl)2(S) + N2 (2)
Table 3. Selected Bond Distances (Å) and Bond Angles (deg) for
trans-[OsIII(tpy)(Cl)2(5-CH3-tetrazolate) (13)
Bonds
Os(1)-Cl(1)
Os(1)-Cl(2)
Os(1)-N(1)
Os(1)-N(12)
Os(1)-N(18)
Os(1)-N(19)
2.3453(18)
2.3425(18)
2.087(5)
1.990(5)
2.085(6)
2.093(5)
N(19)-N(20)
C(22)-N(23)
N(19)-N(23)
N(20)-N(21)
N(21)-C(22)
C(22)-C(24)
1.321(9)
1.328(9)
1.328(8)
1.345(9)
1.323(11)
1.484(11)
-
The general scope of the reaction between 1b and N3 was
investigated by using a variety of nitriles as solvents. This led
to the synthesis and isolation of compounds 4-6. If pyridine
or substituted pyridines are used as solvents the final products
are OsII pyridine complexes (compounds 11 and 12).
Angles
Cl(1)-Os(1)-Cl(2) 178.86(6)
N(12)-Os(1)-N(18)
79.1(2)
[OsVI(tpy)(Cl)2(N)]+ + N3- + S S ) RCN, py8
OsII(tpy)(Cl)2(S) + 2N2 (3)
Cl(1)-Os(1)-N(1)
Cl(1)-Os(1)-N(12)
Cl(1)-Os(1)-N(18)
Cl(1)-Os(1)-N(19)
Cl(2)-Os(1)-N(12)
Cl(2)-Os(1)-N(1)
Cl(2)-Os(1)-N(18)
Cl(2)-Os(1)-N(19)
N(1)-Os(1)-N(12)
89.30(14) N(18)-Os(1)-N(19) 101.1(2)
92.47(15) N(20)-N(21)-C(22) 105.9(6)
89.67(16) N(19)-N(20)-N(21) 107.1(6)
90.55(16) N(20)-N(19)-N(23) 110.9(5)
88.59(15) N(20)-N(19)-N(23) 110.9(5)
90.46(14) N(21)-C(22)-N(23) 111.6(6)
90.96(16) N(21)-C(22)-C(24) 124.3(7)
88.40(16) N(23)-C(22)-C(24) 124.1(7)
3 can be oxidized to 8 with Fc+ salts in CH3CN.
OsII(tpy)(Cl)2(NCCH3) + Fc+ f
OsIII(tpy)(Cl)2(NCCH3) + Fc (4)
79.5(2)
N(19)-N(23)-C(22) 104.4(6)
N(12)-Os(1)-N(19) 177.0(2)
N(1)-Os(1)-N(18) 158.5(2)
N(1)-Os(1)-N(19) 100.5(2)
Trans f cis isomerization of the starting nitrido occurs in
coordinating solvents such as H2O, MeOH, and CH3CN,2 which
provides access to the corresponding cis-nitrile complexes as
afforded a mixture of 3 and trans-OsII(tpy)(Cl)2(15NtN) (2*)
for which ν(15NtN) ) 2062 cm-1 in KBr. The shift is
consistent with the increase in reduced mass. Portions of the
infrared spectra which illustrate the isotopic shift for mixtures
of 2 and 3 and 2* and 3 are provided in the Supporting
-
well. Isomerization of 1b prior to reaction with N3 can be
-
prevented in CH3CN by rapid addition of N3 once 1b is
dissolved.

3614 Inorganic Chemistry, Vol. 37, No. 14, 1998
Demadis et al.
The reaction between 1b and N3- is highly solvent dependent.
In nonpolar solvents such as acetone or CH2Cl2 electron transfer
occurs from N3- to OsVI to give blue trans,trans-(tpy)(Cl)2OsII-
(N2)OsII(Cl)2(tpy) (7) as the product in high yield.
followed by elimination of N2 and formation of cis-[OsVI(tpy)-
(Cl)2(N)]+,
cis-[OsIV(tpy)(Cl)2(N3)] f cis-[OsVI(tpy)(Cl)2(N)]+ + N2
(11)
[OsVI(typ)(Cl)2(N)]+ + N3 (CH ) CdO8
3
2
-
or CH2Cl2
Structural Studies. cis-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (9)
and cis-[OsII(bpy)2(Cl)(NCCH3](PF6) (15). ORTEP diagrams
of the cations of these salts are shown in Figure 1 (9) and Figure
2 (15). Having the crystal structures of 9 and 15 provides an
OsII-Cl and OsIII-Cl bond lengths comparison. Os-Cl bond
lengths in OsIII (9, 2.346(4) and 2.354(4) Å) are shorter than in
OsII (15, 2.4199(6) Å). From literature structures OsIII-Cl bond
lengths fall in the range 2.34-2.36 Å12 and OsII-Cl bond
lengths fall in the range 2.43-2.45 Å.13
In 9 the Os-N22 (tpy, central) bond length is 1.995(12) Å,
and the Os-N11 and Os-N28 (tpy, peripheral) lengths are 2.072-
(12) and 2.063(12) Å, respectively. The shortening of the
“central” M-N(tpy) bond is a characteristic structural feature
of metal-terpyridine complexes in the absence of trans influence
ligands.14 It is dictated by the geometrical constraints of tpy
as a ligand and its inability to span the 180° required for a planar
terdentate ligand. In 9, N28-Os-N11 is 158.7°.
(tpy)(Cl)2OsII(N2)OsII(Cl)2(tpy) + 3/2N2 (5)
In CH3CN the reaction of 1b with N3- in excess takes a dif-
-
ferent course. Initial N3 attack on 1b and solvolysis gives
trans-OsII(tpy)(Cl)2(NCCH3) (3). Once formed, it undergoes a
-
second reaction with N3 by a [3 + 2] cycloaddition to the
bound CH3CN followed by air oxidation to give trans-OsIII(tpy)-
(Cl)2(5-CH3-tetrazolate) (13). The N2-bound isomer shown in
13 is favored on steric grounds. It forms by linkage isomer-
ization of the initially formed N1-bound isomer. It was shown
independently that a reaction occurs between OsII(tpy)(Cl)2-
-
(NCCH3) and N3 in the presence of air to give the same
product.
[OsVI(tpy)(Cl)2(N)]+ + 2N3- + CH3CN f
OsVI(tpy)(Cl)2(5-CH3-tetrazolate) + 2N2 (6)
Bond lengths within the Os-NtCCH3 unit are normal with
Os-N1 2.039(13) Å typical for metal nitriles,15 N1-C2 1.102-
(21) Å consistent with a NtC triple bond, and C2-C3 1.46(3)
Å consistent with a C-C single bond.
In 15 the Os-N(bpy) bond distances range from 2.0365(21)
to 2.0755(21) Å and are similar to Os-N(bpy) bond distances
in [OsII(bpy)3](PF6)2 (2.056(8) Å). The bond lengths within
the Os-NtCCH3 unit are similar to those of 9 with Os-N1
2.0187(22) Å shorter that Os-N1 in 9 due to OsII f NCCH3
π-back-bonding, N1-C2 1.143(3) Å consistent with a NtC
triple bond, and C2-C3 1.455(4) Å, consistent with a C-C
single bond.
In H2O with 2 equiv of N3-, the azido complex cis-OsIII-
(tpy)(Cl)2(N3) (10) forms. Its formation can be rationalized by
initial trans f cis isomerization of trans-[OsVI(tpy)(Cl)2(N)]+,
-
followed by attack of N3 on nitrido 1c to give OsII-N2.
-
Substitution of coordinated N2 by N3 and final air oxidation
would result in 10.
H2O
[OsVI(tpy)(Cl)2(N)]+ + 2N3 air oxdn8
-
OsIII(tpy)(Cl)2(N3) + 2N2 (7)
-
Reaction between 1 and N3 in the presence of CS2 in ace-
trans-[OsIII(tpy)(Cl)2(5-CH3-tetrazolate) (13). The crystal
structure of 13 (for an ORTEP diagram, see ref 1) reveals that
the trans geometry of the starting nitrido is retained. The
5-CH3-tetrazolato ring is coplanar with tpy. N-N and C-N
bond lengths within the tetrazolato ring range from 1.321(9) to
1.345(9) Å consistent with extensive π-electronic delocaliza-
tion.16 The Os-Cl bond lengths are 2.3453(18) and 2.3425-
tone gives the thionitrosyl trans-[OsII(tpy)(Cl)2(NS)](SCN) (14).
[OsVI(tpy)(Cl)2(N)]+ + N3- + CS2 f
[OsII(tpy)(Cl)2(NS)]+ + SCN- + N2 (8)
In acetone, 1b is unreactive with CS2 or S8 separately. Reaction
-
between N3 and CS2 is known to occur to give the 5-thio-
1,2,3,4-thiatriazolato ring anion,
(12) OsIII-Cl bond lengths: (a) Bright, D.; Ibers, J. A. Inorg. Chem. 1969,
8, 1078. (b) Aslanov, L.; Mason, R.; Wheeler, A. G.; Whimp, P. O.
J. Chem. Soc., Chem. Commun. 1979, 30. (c) Champness, N. R.;
Levason, W.; Mould, R. A. S.; Pletcher, D.; Webster, M. J. Chem.
Soc., Dalton Trans. 1991, 2777. (d) Champness, N. R.; Levason, W.;
Pletcher, D.; Spicer, M. D.; Webster, M. J. Chem. Soc., Dalton Trans.
1992, 2201.
It decomposes to give SCN-, N2, and S0.11 In the presence of
1b, nucleophilic attack on OsVItN by the thiolato portion of
the ring takes place with sulfur atom transfer. This is ac-
companied by reduction of OsVI to OsII and formation of
thionitrosyl 14.
Finally, reaction between 10 and CeIV proceeds via initial
one-electron transfer,
(13) OsII-Cl bond lengths: (a) Chakravarty, A. R.; Cotton, F. A.;
Schwotzer, W. Inorg. Chim. Acta 1984, 84, 179. (b) Cotton, F. A.;
Diebold, M. P.; Matusz, M. Polyhedron 1987, 6, 1131. (c) Robinson,
P. D.; Ali, I. A.; Hinckley, C. C. Acta Crystallogr. 1991, C47, 651.
(d) Levason, W.; Champness, N. R.; Webster, M. Acta Crystallogr.
1993, C49, 1884.
(14) (a) Beck, J.; Schweda, E.; Stra¨hle, J. Z. Naturforsch. 1985, B40, 1073.
(b) Bardwell, D. A.; Cargill Thompson, M. W.; McCleverty, J. C.;
Ward, M. D. J. Chem. Soc., Dalton Trans. 1996, 873. (c) Constable,
E. C.; Edwards, A. J.; Haire, G. R.; Hannon, M. J.; Raithby, P. R.
Polyhedron 1998, 17, 243. (d) Kozˇ´ısˇek, J.; Jarom´ır, M.; Baloghova´;
Valigura, D. Acta Crystallogr. 1997, C53, 1813. (e) Constable, E. C.
Metals and Ligand ReactiVity; VCH Publishers: New York, 1996,
and references therein.
cis-OsIII(tpy)(Cl)2(N3) + CeIV
f
cis-[OsIV(tpy)(Cl)2(N3)]+ + CeIII (10)
(15) (a) Storhoff, B. N. Coord. Chem. ReV. 1977, 23, 1. (b) Hodges, L.
M.; Sabat, M.; Harman, W. D. Inorg. Chem. 1993, 32, 371.
(16) (a) Moore, D. S.; Robinson, S. D. AdV. Inorg. Chem. 1988, 32, 171.
(b) Butler, R. N. In Tetrazoles; Katritzky, A. R., Rees, C. W., Eds.;
Comprehensive Heterocyclic Chemistry 5; Pergamon Press: Oxford,
U.K., 1984; p 791. (c) Koldobskii, G. I.; Ostrovskii, V. A. Russ. Chem.
ReV. 1994, 63, 797.
(11) (a) Lieber, E.; Pillai, C. N.; Ramachandran, J.; Hites, R. D. J. Org.
Chem. 1957, 22, 1750. (b) Lieber, E.; Oftedahl, E.; Rao, C. N. R. J.
Org. Chem. 1963, 28, 194. (c) Browne, A. W.; Hoel, A. B.; Smith,
G. B. L.; Swezey, F. H. J. Am. Chem. Soc. 1923, 45, 2541. (d) Carbon
Disulphide in Organic Chemistry; Dunn, A. D., Rudorf, W.-D., Eds.;
Ellis Horwood Ltd.: New York, 1989.

New Route to Os(II) Polypyridyl Complexes
Inorganic Chemistry, Vol. 37, No. 14, 1998 3615
(18) Å, consistent with OsIII.12 Shortening of the central Os-
N(tpy) bond length to 1.990(5) Å is apparent, compared with
the peripheral Os-N(tpy) bond lengths of 2.087(5) and 2.085-
(5) Å. The Os-N(tetr) bond length, 2.093(5) Å, is similar to
other metal tetrazolate complexes.17 To our knowledge, this is
the first Os-tetrazolato complex which has been isolated and
structurally characterized.
typical for metal azido complexes.22 14 exhibits an intense band
at 1295 cm-1 assignable to ν(NtS) (ν(15NtS) 1265 cm-1).
Several Os thionitrosyl complexes have been characterized by
infrared spectroscopy, and these results have been reviewed
elsewhere.23 The usual range for ν(NtS) is 1150-1400 cm-1
.
In the infrared spectrum of 13, bands at 1094 and 1295 cm-1
appear that can be assigned to tetrazolate ring modes as proposed
previously.24 Additional ring modes are expected but are
apparently obscured by tpy bands.
trans-[OsII(tpy)(Cl)2(NS)](SCN) (14). The crystal structure
of 14 (Figure 3) shows that the Cl- ligands are in the trans
configuration, a feature retained from 1. Os-Cl bond distances
are 2.366(2) and 2.360(2) Å. The Os-N(S) and the N-S bond
distances are 1.834(7) and 1.459(8) Å. The N-S bond length
in the NS+ ion is 1.495 Å.18 The Os-N-S is almost linear,
at 178.5(5)° consistent with thionitrosyl coordinated as “NS+”
rather than “NS-”. In structurally characterized OsII(PPh3)2-
(Cl)3(NS), Os-N(S) and the N-S bond distances are 1.779(9)
and 1.503(10) Å, respectively, and Os-N-S is 180.0(1)°.19
For comparison, in trans-[OsII(tpy)(Cl)2(NO)](BF4) the Os-
N(O) and N-O bond distances are 1.704(14) and 1.188(19) Å
and Os-N-O is 176.6(10)°.4 Os-N(thionitrosyl) bond
lengths in the literature fall in the range of 1.73-1.84 Å,19
consistent with sp hybridization if the NS ligand is treated as a
3e- donor. This predicts multiple bond character in the M-N
bond in agreement with the short M-N bond distances and the
linearity of the thionitrosyl.
In the electrochemical studies (Table 6), the OsII and OsIII
nitrile complexes exhibit waves corresponding to OsIII/OsII and
OsIV/OsIII couples. More specifically, for 3 a reversible OsIII/
OsII couple appears at E1/2 ) +0.15 V and a reversible OsIV/
OsIII couple at E1/2 ) +1.46 V, in CH2Cl2, vs SSCE in 0.1 M
TBAH. Similar results were obtained for OsII nitriles 4-6. For
8, a reversible OsIII/OsII couple appears at E1/2 ) +0.04 V and
a reversible OsIV/OsIII couple at E1/2 ) +1.37 V, in CH3CN, vs
SSCE in 0.1 M TBAH. For 15 there are reversible OsIII/OsII
and OsIV/OsIII couples at E1/2 ) +0.41 V and E1/2 ) +1.87 V,
respectively, in CH3CN, vs SSCE in 0.1 M TBAH.7 Ligand-
based (bpy) reductions appear at -1.45 and -1.72 V.
In cyclic voltammograms of 10, a reversible OsIII/OsII wave
appears at E1/2 ) +0.06 V and chemically irreversible OsIV/
OsIII couple at Ep,a ) +0.85 V in CH3CN. After minutes, waves
corresponding to the OsIII/OsII and OsIV/OsIII couples of 3
appear. Apparently, in this solvent N3- f OsIII intramolecular
electron transfer takes place to give 3 and N2. The OsII pyridine
complexes exhibit E1/2 values for OsIII/OsII and OsIV/OsIII
couples at +0.12 and +1.49 V, for 11, and +0.08 and +1.46
V, for 12, respectively. In cyclic voltammograms of 7 in DMF,
reversible OsIII-OsII/OsII-OsII and OsIII-OsIII/OsIII-OsII couples
appear at +0.21 and +0.77 V vs SSCE (∆E1/2 ) 560 mV).
The propereties of the mixed-valence form have been described
and are discussed elsewhere.6
Spectroscopic and Electrochemical Studies. The results
of UV-vis and electrochemical studies are compiled in Table
6. The UV-vis spectra of the OsII complexes are dominated
by intense OsII f tpy or OsII f bpy MLCT bands in the visible
region and intense π f π*(tpy) or π f π*(bpy) bands in the
UV region.6,7
For the OsII and OsIII nitrile complexes ν(CtN) appears in
the infrared at 2190-2260 cm-1 of medium-to-strong intensity,
consistent with Os-N end-on binding.20 ν(NtN) for 2 appears
at 2090 cm-1, shifted by 28 cm-1 to 2062 cm-1 in 2* (calculated
33 cm-1). Several other N2 complexes exhibit intense ν(NtN)
bands in this region.21 For comparison, in OsII(tpm)(Cl)2(N2)
ν(NtN) appears at 2068 cm-1 in KBr (ν(15Nt14N) at 2032
cm-1).1 In µ-N2-bridged 7 a very weak ν(NtN) stretch appears
at 2035 cm-1 in KBr (ν(15Nt15N) appears at 1972 cm-1).
E1/2 values for the OsIII/II and OsIV/III couples of 13 are -0.26
and +1.01 V, respectively, in 0.1 M TBAH, vs SSCE, in
DMSO. In cyclic voltammograms of 14 in CH3CN, a reversible
ligand-based reduction wave is observed at -0.30 V vs SSCE
in 0.1 M TBAH. Similar ligand-based reductions have been
observed in OsII-NO complexes.25 No oxidation waves are
observed for 14 to the solvent limit.
For 10 a very intense ν(N3) vibration appears at 2041 cm-1
,
Discussion
(17) (a) Gaughan, A. P.; Bowman, K. S.; Dori, Z. Inorg. Chem. 1972, 11,
601. (b) Jime´nez-Sandoval, O.; Cea-Olivares, R.; Herna´ndez-Ortega,
S.; Silaghi-Dumitrescu, I. Heteroatom Chem. 1997, 8, 351. (c)
Wijnands, P. E. M.; Wood, J. S.; Reedijk, J.; Maaskant, W. J. A. Inorg.
Chem. 1996, 35, 1214. (d) Gallardo, H.; Begnini, I. M.; Vencato, I.
Acta Crystallogr. 1997, C53, 143. (e) van den Heuvel, E. J.; Franke,
P. L.; Verscoor, G. C.; Zuur, A. P. Acta Crystallogr. 1983, C39, 337.
(18) Barrow, R. F.; Warm, R. J.; Fitzerald, A. G.; Fyoffe, B. D. Trans.
Faraday Soc. 1964, 60, 294.
In this manuscript we document the extraordinarily rich
reactivity chemistry that exists between 1 and N3
summarized in Figure 4. In all cases, the basic chemistry is
the same, attack of a redox nucleophile on a coordinated ligand,
in competition with electron transfer.
-
. It is
(19) Roesky, H. W.; Pandey, K. K.; Clegg, W.; Noltemeyer, M.; Sheldrick,
G. M. J. Chem. Soc., Dalton Trans. 1984, 719.
(22) (a) Kane-Maguire, L. A. P.; Sheridan, P. S.; Basolo, F.; Pearson, R.
G. J. Am. Chem. Soc. 1970, 92, 5865. (b) Reed, J. L.; Gafney, H. D.;
Basolo, F. J. Am. Chem. Soc. 1974, 96, 1363. (c) Dori, Z.; Ziolo, R.
F. Chem. ReV. 1973, 73, 247. (d) Azides and Nitrenes: ReactiVity
and Utility, Scriven, E. F. V., Ed.; Academic Press: Orlando, FL,
1984; and references therein. (e) Chemistry of Pseudohalides; Golub,
A. M., Ko¨hler, H., Eds.; Elsevier Publishers: Amsterdam, 1986. (f)
The Chemistry of Halides, Pseudohalides, and Azides (Chemistry of
Functional Groups. Supplement D2); Patai, S., Rappoport, Z., Eds.;
Interscience: Chichester, U.K., 1995.
(23) (a) Roesky, H. W.; Pandey, K. K. AdV. Inorg. Chem. Radiochem. 1983,
26, 337 and references therein. (b) Pandey, K. K. Prog. Inorg. Chem.
1992, 40, 445 and references therein.
(24) (a) John, E. O.; Willett, R. D.; Scot, B.; Kirchmeier, R. L.; Shreeve,
J. M. Inorg. Chem. 1989, 28, 893. (b) Franke, P. L.; Groeneveld, W.
L. Transition Met. Chem. 1981, 6, 54.
(20) (a) Sekine, M.; Harman, W. D.; Taube, H. Inorg. Chem. 1988, 27,
3604. (b) Johnson, A.; Taube, H. J. Indian Chem. Soc. 1989, 66, 503.
(c) Endres, H. In ComprehensiVe Coordination Chemistry; Wilkinson,
G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamor: London, 1987;
Vol. 2, p 261. (d) Nakamoto, K. Infrared and Raman Spectra of
Inorganic and Coordination Compounds; Wiley-Interscience: New
York, 1986.
(21) (a) Henderson, R. A.; Leigh, G. J.; Pickett, C. J. AdV. Inorg. Chem.
Radiochem. 1983, 27, 197 and references therein. (b) Hidai, M.;
Mizobe, Y. Chem. ReV. 1995, 95, 1115 and references therein. (c)
Fergusson, J. E.; Love, J. L.; Robinson, W. T. Inorg. Chem. 1972,
11, 1662. (d) Lay, P. A.; Taube, H. Inorg. Chem. 1989, 28, 3561. (e)
Albertin, G.; Antoniutti, S.; Baldan, D.; Bordignon, E. Inorg. Chem.
1995, 34, 6205. (f) Bianchini, C.; Linn, K.; Masi, D.; Peruzzini, M.;
Polo, A.; Vacca, A.; Zanobini, F. Inorg. Chem. 1993, 32, 2366. (g)
Dilworth, J. R.; Richards, R. L. In ComprehensiVe Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A.; Abel, E. W., Eds.;
Pergamon: Oxford, U.K., 1982; Vol. 8, p 1073.
(25) (a) Murphy, W. R., Jr.; Takeuchi, K. J.; Meyer, T. J. J. Am. Chem.
Soc. 1982, 104, 5817. (b) Pipes, D. W.; Meyer, T. J. Inorg. Chem.
1984, 23, 2466. (c) Ooyama, D.; Nagao, H.; Ito, K.; Nagao, N.; Howell,
F. S.; Mukaida, M. Bull. Chem. Soc. Jpn. 1997, 70, 2141.

3616 Inorganic Chemistry, Vol. 37, No. 14, 1998
Demadis et al.
IR bands,
Table 6. UV-Vis, Electrochemical (0.1 M TBAH vs SSCE), and Infrared Data for Compounds 3-15
solvent for
cyclic
voltammetry
E
1/2(OsIV/III), E1/2(OsIII/II), other
complex or salt
λ
max, nm (ꢀ, M-1cm-1
)
V
V
waves cm-1 (in KBr)
trans-OsII(tpy)(Cl)2(NCCH3) (3)
in DMF: 736 (2900),
662 (4100), 580 (6550),
482 (8300), 418 (7300),
372 (9200), 328 (28 100),
284 (23 100), 274 (22 200)
in DMF: 728 (1920),
648 (3850), 578 (5850),
474 (7090), 418 (6760),
368 (9940), 326 (22 930),
282 (21 370), 272 (22 440)
in DMF: 736 (3090),
658 (4270), 576 (6760),
480 (8410), 420 (7700),
364 (9580), 326 (31 660),
284 (25 000), 272 (24 470)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
DMF
+1.46
+0.15
2250, ν(CtN)
trans-OsII(tpy)(Cl)2(NCC5H6) (4)
+1.54
+1.51
+1.54
+0.20
+0.18
+0.30
2204, ν(CtN)
trans-OsII(tpy)(Cl)2-
(NCCH2CH2CH3) (5)
2242, 2227,
ν(CtN)
trans-OsII(tpy)(Cl)2(NCCHdCH2) (6) in DMF: 722 (1740),
648 (2610), 554 (4720),
+0.87a 2190, ν(CtN);
1606, ν(CdC)
480 (5050), 406 (4970),
368 (6360), 330 (23 560),
284 (16 440), 272 (15 510)
in DMF: 885 (9100),
660 (14 500), 592 (16 000),
444 (10 800), 394 (13 000),
364 (16 400), 332 (46 600),
272 (48 800)
trans,trans-(tpy)(Cl)2OsII-
(N2)OsII(Cl)2(tpy) (7)
+0.21,b 2035, ν(NtN)
+0.77c
trans-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (8) in CH3CN: 616 (400),
540 (1200), 516 (1700),
CH3CN
+1.37
+1.38
+0.04
+0.03
2256, 2213,
ν(CtN)
488 (2500), 456 (3200),
438 (3100), 396 (2400),
354 (sh, 7900), 318 (24 000),
276 (19 400), 230 (36 300)
cis-[OsIII(tpy)(Cl)2(NCCH3)](PF6) (9)
in CH3CN: 604 (390),
500 (1440), 440 (3500),
374 (2950), 326 (16 290),
306 (18 800), 282 (18 720),
274 (12 990), 226 (26 300)
in H2O: 660 (2750),
470 (4320), 402 (3940),
332 (10 549, 310 (14 200),
272 (14 440), 224 (18 690)
in DMF: 754 (990), 680 (1330),
592 (2420), 496 (2760),
418 (3240), 380 (4160),
328 (8000), 275 (9000),
272 (9100)
CH3CN
2326, 2283,
(CtN)
cis-OsIII(tpy)(Cl)2(N3) (10)
trans-OsII(tpy)(Cl)2(py) (11)
CH3CN
CH2Cl2
+0.85
+1.49
+0.06
+0.12
2041, ν(N3)
trans-OsII(tpy)(Cl)2(4-(CH3)3C-py) (12) in DMF: 752 (800), 678 (1390),
CH2Cl2
+1.46
+1.01
+0.08
-0.26
592 (2140), 500 (2110),
420 (2510), 380 (3290),
330 (7910), 276 (8900),
270 (8980)
in DMSO: 570 (1350),
526 (1400), 472 (1900),
406 (1800), 324 (10 300),
278 (9500)
in CH3CN: 742 (110), 522 (340),
430 (600), 362 (3800),
278 (10 900), 240 (16 300),
208 (12 800)
trans-[OsIII(tpy)(Cl)2(5-CH3-tetr) (13)
trans-[OsII(tpy)(Cl)2(NS)](SCN) (14)
CH3CN
CH3CN
CH3CN
1094, 1295,
ν(CH3-tetr)
-0.30d 1295, ν(NS);
2047, ν(SCN)
cis-[OsII(bpy)2(Cl)(NCCH3](PF6) (15) in CH3CN: 690 (2800), 650 (sh),
+1.87
+0.21
2255, ν(CtN)
495 (8700), 411 (8200),
375 (sh), 350 (8300),
293 (54 000), 255 (sh), 243 (sh),
236 (24 000)
aThe origin of this wave is uncertain. It could be due to oxidation of bound NCCHdCH2. b OsIII-OsII/OsII-OsII couple. c OsIII-OsIII/OsIII-OsII
couple. d Thionitrosyl-based couple.

New Route to Os(II) Polypyridyl Complexes
Inorganic Chemistry, Vol. 37, No. 14, 1998 3617
Figure 4. Reactivity between trans-[OsVI(tpy)(Cl)2(N)]+ (1) and N3
.
-
The fact that reaction between 1 and N3- occurs by attack of
N3- on the nitrido ligand with retention of the nitrido N is shown
by the result of the 15N-labeling experiment and the appearance
of Os(tpy)(Cl)2(15N14N). Although we have no spectroscopic
evidence for its formation, this reaction presumably occurs via
an Os-N4 intermediate which decomposes to give bound and
free N2,
occurring between the σN-based lone pair on the nitrido and
(tpy)(Cl)2OsVI(N)+ + N3- f [(tpy)(Cl)2Os(NNNN)] f
(tpy)(Cl)2Os-N2 + N2 (12)
In a formal sense this reaction involves the transfer of N- from
-
N3 to the nitrido atom with multiple intramolecular electron
transfer to give OsII-N2. Dehnicke et al. have isolated and
structurally characterized a W dimer in which there is an N4
bridging ligand.26 Except for the 15N-labeling experiment, we
have no detailed mechanistic information about how this reaction
proceeds. However, there are two reasonable possibilities. Both
are speculative since there is no evidence for an intermediate.
the lowest antibonding level on N3- without coordination sphere
expansion,
1 is a d2 OsVI complex with electronic configuration
2
0
0
dπ1 dπ2 dπ3 . If the z axis is defined to lie along the Os-N
bond, dπ2 and dπ3 are largely dxz, dyz, with considerable Os-N
antibonding character because of extensive mixing with the filled
2px, 2py orbitals of the nitrido ligand. With dπ2, dπ3 empty,
the lowest available levels for electron pair attack on the nitrido
are at the metal with, possibly, coordination sphere expansion,
followed by intracoordination sphere N-N coupling. Alterna-
tively, the initial electronic interaction could be envisioned as
This would be followed by intramolecular electronic redistribu-
tion and N-N bond cleavage.
(26) Massa, W.; Kujanek, R.; Baum, G.; Dehnicke, K. Angew. Chem., Int.
Ed. Engl. 1984, 23, 149.

3618 Inorganic Chemistry, Vol. 37, No. 14, 1998
Demadis et al.
-
The reaction between 1 and N3 is solvent dependent. In
OsIV to azide, to give OsVI, stabilized by Os-N multiple
bonding, and N2. It returns the complex to the original nitride
form.
acetone or CH2Cl2 the product is the µ-N2 complex trans,trans-
(tpy)(Cl)2OsII(N2)OsII(Cl)2(tpy) (7). It presumably forms by
initial electron transfer to give OsV,
The lability of N2 in OsII-N2 makes it a synthetically useful
intermediate. We exploited this aspect of the chemistry in the
preparation of the series of nitriles, 3-6 and the series of
pyridines, 11 and 12, by using the entering group as solvent.
Although somewhat restricted in scope, this represents a
synthetically useful, high-yield route to a series of polypyridyl
complexes of OsII which are otherwise difficult to prepare.
The formation of the tetrazolate complex is also a stepwise
reaction, first involving Os-N2 formation, eq 1, followed by
solvolysis, eq 2, to give the CH3CN complex 3. The bound
CH3CN is activated toward attack by N3-. Attack of N3- most
likely takes place at OsII-NCCH3, because 3 is air stable.
Metal-tetrazolates form by cycloaddition either by reaction of
[OsVI(tpy)(Cl)2(N)]+ + N3- f OsV(tpy)(Cl)2(N) + N3
0
(15)
followed by N-N coupling,
OsV(tpy)(Cl)2(N) f 1/2(tpy)(Cl)2OsII(N2)OsII(Cl)2(tpy)
(16)
N30 f 3/2N2
(17)
-
N3 with metal nitriles30 or by reaction of nitriles with metal
The solvent effect in this case may simply reflect the solvent
azides.31 Linkage isomerization of the resulting metal-tetra-
zolate is common and gives the least sterically hindered
structure.32 Based on mechanistic studies on related reactions,
the pathway for formation of 13 can be described as initial
cycloaddition to give the N1-bound isomer, followed by isomer-
ization to the more stable N2-bound isomer.
0
dependences of the potentials for the N3-/N3 and
[OsVI(tpy)(Cl)2(N)]+/0 couples. The ions are favored in polar
solvents which decreases the driving force for electron transfer.
It has been reported that E°′(N3-/N3 ) ) 0.73 V in CH3CN vs
0
SSCE in 0.1 M TBAH at a Pt electrode.27 In polar solvents,
the driving force and rate constant for electron transfer are
decreased allowing the electron pair interactions in eq 13 or 14
to compete.
Once formed in CH3CN, the N2 complex is labile toward
loss of N2 and solvolysis on a time scale of minutes. This is
somewhat surprising since the coordination environment is
relatively electron rich. The potential for the trans-[Os(tpy)-
(Cl)2(NH3)]+/0 couple is -0.10 V vs SSCE in CH3CN. By
contrast, we have found recently that the N2 complex OsII(tpm)-
(Cl)2(N2) (tpm ) tris(1-pyrazolyl)methane) formed by reaction
-
between N3 and the corresponding nitrido is stable under the
same conditions.1
The reaction between 1 and 2-fold excess N3 in H2O can
-
be rationalized as occurring, in the initial stages, as in CH3CN
but preceded by trans f cis isomerization, which is rapid.
-
Presumably, attack of N3 on the nitrido nitrogen of the cis
isomer is followed by solvation to give OsII-H2O. Anation of
The final product is the OsIII complex formed by air oxidation.
Formation of the OsII thionitrosyl also involves attack of a
redox nucleophile on the nitrido, in this case by initial cyclic
the aqua complex by the second N3 would give OsII-N3 and
-
subsequent air oxidation of OsII to OsIII final product.
Ware and Taube studied the same reaction and reported trans-
[OsIII(tpy)(Cl)2(H2O)]+ as the product in 10% yields.28 How-
ever, these authors note that when the reaction mixture was
passed through a Sephadex SP cation exchange column, a
considerable amount of colored material remained on the
column, presumably 10.
-
adduct formation between CS2 and N3 to give 5-thio-1,2,3,4-
thiatriazolato anion, eq 9. This adduct is known to be unstable
and explosive.11 The only evidence we have for its formation
is the literature precedence, the absence of reaction between 1
-
and CS2 in acetone, and the fact that the reaction between N3
and 1 in acetone gives the µ-N2 dimer trans,trans-(tpy)(Cl)2-
OsII(N2)OsII(Cl)2(tpy) (7). Once the adduct forms, it apparently
attacks the electrophilic nitrido in 1. The N atom of the nitrido
group is retained in the thionitrosyl as shown by the 15N-labeling
experiment (see Experimental Section). Initial attack on the
nitrido is followed by internal electronic redistribution and net
electron transfer,
The conversion of 10 to 1 by CeIV oxidation, eqs 10 and 11,
proceeds cleanly with evolution of N2 (as evidenced by the
rigorous effervesence). This is a known reaction for other metal
azides to give metal nitrides which occur with elimination of
N2.29 It involves a net intramolecular two-electron transfer from
(27) (a) Brown, G. M.; Callahan, R. W.; Meyer, T. J. Inorg. Chem. 1975,
14, 1915. (b) Latimer, W. M. Oxidation Potentials, 2nd ed.; Prentice
Hall: Englewood Cliffs, NJ, 1952.
(30) (a) Hall, J. H.; Lopez de la Vega, R.; Purcell, W. L. Inorg. Chim.
Acta 1985, 102, 157. (b) Ros, R.; Renaud, J.; Roulet, R. J. Organomet.
Chem. 1976, 104, 393.
(31) (a) Kreutzer, P.; Weis, C.; Boheme, H.; Kemmerich, T.; Beck, W.;
Spencer, C.; Mason, R. Z. Naturforsch. 1972, B27, 745. (b) Beck,
W.; Fehlhammer, W. P.; Angew. Chem., Int. Ed. Engl. 1967, 6, 169.
(c) Paul, P.; Nag, K. Inorg. Chem. 1987, 26, 2969.
(32) (a) Takach, N. E.; Holt, E. M.; Alcock, N. W.; Henry, R. A.; Nelson,
J. H. J. Am. Chem. Soc. 1980, 102, 2968. (b) Ellis, W. R., Jr.; Purcell,
W. L. Inorg. Chem. 1982, 21, 834. (c) Hubinger, S.; Purcell, W. L.
Inorg. Chem. 1991, 30, 3707. (d) Jackson, W. G.; Cortez, S. Inorg.
Chem. 1994, 33, 1921.
(28) Ware, D. C.; Taube, H. Inorg. Chem. 1991, 30, 4605.
(29) (a) Barner, C. J.; Collins, T. J.; Mapes, B. E.; Santarsiero, B. D. Inorg.
Chem. 1986, 25, 4322. (b) Chatt, J.; Falk, C. D.; Leigh, G. J.; Paske,
J. A. J. Chem. Soc. A 1969, 2288. (c) Doedens, R. J.; Ibers, J. A.
Inorg. Chem. 1967, 6, 204. (d) Bereman, R. D. Inorg. Chem. 1972,
11, 1149. (e) Arshankow, S. J.; Poznjak, A. L. Z. Anorg. Allg. Chem.
1981, 481, 201. (f) Dehnicke, K. AdV. Inorg. Chem. Radiochem. 1983,
26, 169. (g) Dehnicke, K.; Stra¨hle, J. Angew. Chem., Int. Ed. Engl.
1992, 31, 955. (h) Groves, J. T.; Takahashi, T. J. Am. Chem. Soc.
1983, 105, 2073. (i) Bevan, P. C.; Chatt, J.; Dilworth, J. R.; Henderson,
R. A.; Leigh, G. J. J. Chem. Soc., Dalton Trans. 1982, 821.

New Route to Os(II) Polypyridyl Complexes
Inorganic Chemistry, Vol. 37, No. 14, 1998 3619
Re(CO)5Br + (NS)(SbF6) f
[Re(NS)(CO)5]2+ + SbF6- + Br- (23)
There is also a coordination chemistry of CS2N3-. Metal-azido
complexes are known to undergo reaction with CS2 to give
isothiocyanates (N-bound), S8, and N2, e.g.,36
The SCN- formed acts as the counterion for 14 and was
identified by IR and X-ray crystallography.
This is the first example of preparation of metal thionitrosyls
with the sulfur atom coming from CS2. Common methods
available for the preparation of metal thionitrosyls include (a)
reaction between metal nitridos and sulfur transfer reagents,33
There is a complementary chemistry based on reaction between
metal-CS2 complexes and N3-, also to give metal isothiocy-
anates (N-bound).37
[OsVI(N)(Cl)4]- + S2Cl2 + 2py f
OsII(NS)(py)2(Cl)3 + Cl- (20)
Mo(N)(S2CNR2)3 + 1/8S8 f Mo(NS)(S2CNR2)3 (21)
Acknowledgments are made to the National Science Foun-
dation under Grant No. CHE-9503738.
(b) transfer of NS from NS precursors,19,34
Supporting Information Available: Portions of infrared spectra
with isotopic shifts for 2, 3, 2*, and 3*, text providing additional details
of the crystallographic analyses of compounds 9 and 13-15, a fully
labeled ORTEP diagram, and tables of atomic coordinates and B values,
isotropic thermal parameters, and bond distances and angles (29 pages).
Ordering information is given on any current masthead page.
Os(Cl)2(PPh3)3 + (NSCl)3 f Os(NS)(Cl)3(PPh3)2
(22)
and (c), transfer of NS+,35
(33) Bishop, M. W.; Chatt, J.; Dilworth J. R. J. Chem. Soc., Chem.
Commun. 1979, 1.
(34) (a) Lu, J.; Clarke, M. J. Inorg. Chem. 1990, 29, 4123. (b) Pandey, K.
K.; Paleria, V.; Nehete, D. T. Synth. React. Inorg. Met. Org. Chem.
1990, 20, 1169. (b) Bohle, D. S.; Hung, C.-H.; Powell, A. K.; Smith,
B. D.; Wocadlo, S. Inorg. Chem. 1997, 36, 1992.
IC9800280
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Busetto, L.; Palazzi, A.; Ros, R. Inorg. Chim. Acta 1975, 13, 233.
(37) (a) Schenk, W. A.; Schwietzke, T.; Mu¨ller, H. J. Organomet. Chem.
1982, 232, C41. (b) Schenk, W. A.; Ku¨mmerle, D. J. Organomet.
Chem. 1986, 303, C25.
(35) Mews, R.; Liu, C. Angew. Chem., Int. Ed. Engl. 1983, 22, 158.